I currently am running a a 489 suregrip case with 3.91 gears and 27" tall tires on my '66 Coronet. At 55mph I am turning 2800 RPM and at 65mph turning 3200. I plan on driving this car to various gatherings and shows around the midwest and want a lower highway cruising RPM along with better MPG so I just recently picked up a 489 open with 3.23's which should get me down to 2150 at 55mph and 2450 at 65mph

Just my